TypeError in case COREG or COREG_LOCAL is called with an in-memory reference or target image and path_out is set to 'auto'.

In case COREG or COREG_LOCAL is called with an in-memory reference or target image and path_out is set to 'auto', the dollowing exception is raised:

Error
Traceback (most recent call last):
  File "/home/gfz-fe/python_GFZ/python/lib/python3.6/unittest/case.py", line 59, in testPartExecutor
    yield
  File "/home/gfz-fe/python_GFZ/python/lib/python3.6/unittest/case.py", line 605, in run
    testMethod()
  File "/home/gfz-fe/scheffler/python/arosics/tests/test_COREG.py", line 116, in test_shift_calculation_inmem_gAs_path_out_auto
    v=True))
  File "/home/gfz-fe/scheffler/python/arosics/tests/test_COREG.py", line 61, in run_shift_detection_correction
    CR = COREG(ref, tgt, **params)
  File "/home/gfz-fe/scheffler/python/arosics/arosics/CoReg.py", line 285, in __init__
    self._set_outpathes(im_ref, im_tgt)
  File "/home/gfz-fe/scheffler/python/arosics/arosics/CoReg.py", line 349, in _set_outpathes
    dir_out, fName_out = os.path.dirname(path_im_tgt), ''
  File "/home/gfz-fe/python_GFZ/python/lib/python3.6/posixpath.py", line 154, in dirname
    p = os.fspath(p)
Exception: expected str, bytes or os.PathLike object, not NoneType